Adolescent Nutrition

Abstract

Adolescence is characterized as a phase of great physical, emotional and social changes, through complex, continuous and non-uniform events, which promote the necessary physiological changes to transform the individual into an adult. For this, the human being suffers multiple influences from the environment that, associated with their genetic potential, will trigger processes of accelerated growth, changes in body composition and sexual maturation. During adolescence, a pubertal outbreak occurs, responsible for increasing weight, height and changes in body composition, adding bone tissue, fat and muscle mass. Due to all the physical changes that occur at this stage of life, adolescence is a period in which individuals have specific nutritional needs that must be observed so that hormonal stimuli and interaction with the environment can play a fundamental role in modulating growth and development. This article presents some characteristics involved in the adolescent's nutrition process, seeking to highlight aspects related to energy intake, macronutrients and micronutrients. In addition, some characteristics related to eating behavior are discussed and aspects of encouraging the consumption of healthy foods are discussed, with support from the family, the school and the whole society.

Keywords: Adolescence; Nutrition; Adolescent nutrition; Eating behavior.

Introduction

Adolescence, from a chronological point of view, comprises the second decade of life and is characterized as a phase of great physical, emotional, and social changes that the individual goes through, evolving from childhood to adulthood. For this, the human being suffers multiple influences from the environment, which acting on his genetic potential will trigger the processes of accelerating growth, modification of body composition and sexual maturation, culminating in the physical and emotional structuring of an organism that will reach its full productive capacity [1].

The process of growth and development of the human being is a complex, continuous and non-uniform event, which promotes the necessary physiological changes to transform the individual into an adult being. Among the stages of growth with increased speed, adolescence stands out as the second fastest period, when the pubertal spurt occurs, which is responsible for increasing weight, height and changes in body composition, adding to bone tissue, fat and muscle mass [2,3]. Due to all the physical changes that occur during this stage of life, adolescence is a period in which individuals have specific nutritional needs that must be observed so that hormonal stimuli and interaction with the environment can play a fundamental role in modulating growth and development [4].

Nutritional needs

Individual variability, anabolic increase, and adolescent maturation determine that their nutritional needs vary according to the stages of pubertal development. Hormonal, genetics and environmental factors continuously interact to modify the growth. Regarding weight, males, by testosterone action, have a greater amount of muscle mass, while greater fat deposition is seen among girls, due to the effects of estrogen and progesterone [5].

Energy

In addition to the energy required for basic life-sustaining processes (basal metabolism), caloric requirements are high and determined by physical activity, growth and accumulation of lean tissue [6]. Energy needs aim to meet all demands and vary according to sex, age, height, level of physical activity, climate and other ecological factors, with the period of greatest caloric intake coinciding with the peak of maximum growth speed. The caloric requirement of adolescent males is higher than that of females, owing to greater increases in height, weight, and lean body mass. Boys’ height velocity begins one-two years after girls and takes more time [7]. Up to 13 years of age, 2100 Kcal/day is required for females and 2300 Kcal/day for males; from the age of 14, these needs increase to 2400 Kcal/day and 3100 Kcal/day, respectively. In special, during the puberty spurt occurs a 12% increase in basal metabolic rate and 18% increase in total energy expenditure, accounted for largely by the increase in fat-free mass. The energy balance of an adequate diet must be distributed in at least 50% of the total calorie from carbohydrate, 35% from fat and 15% of protein [7,8].

Protein

Protein requirements are necessary to maintain the body mass and to obtain adequate pubertal spurt and growth. A healthy diet should contain 10% to 30% of calories based on protein intake, of which 2/3 should be of animal origin and 1/3 of high biological value [9]. While for females the daily amounts vary little, between 44 to 46 grams/day, for males between 46 and 59 gram/day are necessary for a complete corporal satisfaction. It is important to check the relationship between the amount of protein and the total energy ingested, because when energy is insufficient, the protein can be used as an energy substrate, reducing its availability for primary functions [10].

Carbohydrate

Carbohydrates must contribute with approximately 50% of the total energy and be provided by naturally occurring sugars (preferably amylose and amylopectin) and added sugar as mono and disaccharides. It is important to consider the need to ingest complex carbohydrates, which also constitute an important source of fiber. Refined sugars, however, should be limited to less than 8 to 10% of total energy because of their relationship to excessive weight gain [6,9].

Fat

Fat in the diet is essential for absorption of fat-soluble vitamins and production of cholesterol and sex hormones. It should also be considered that atherosclerotic lesions in the aorta and coronary arteries can begin to appear early and are positively associated with total elevation and low-density lipoprotein cholesterol [11]. Therefore, in addition to the energy needs supplied by fats, the quality of this nutrient must also be observed. About 35% and no less than 20% of calories must be supplied by fat distributing in 7% by saturated fats, 10% to 15% by monounsaturated fat, 13% by polyunsaturated fats, less than 1% from saturated trans fat and no more than 300 mg/day of cholesterol [9]. The diet must also meet the needs for essential fatty acids (linoleic and linolenic) from plant sources, such as nuts, soybean oils, corn, canola, cotton and sesame.

Fiber

Dietary fiber is a vegetable food residue, resistant to hydrolysis by digestive enzymes, which can reduce cholesterol absorption and produce short-chain fatty acids, causing satiety and increasing stool volume. The beneficial effects of the consumption of fruits and vegetables are related to the promotion of health and prevention of diseases, providing food with a reduction in the total energy levels, energy density, and the supply of vitamins and minerals. One of the factors that interfere with their consumption by adolescents is the low palatability. It is desirable that the diet is composed by whole foods with high fiber content from vegetables, legumes and fruits. While for adolescents up to 13 years of age, about 30 grams of fiber daily is sufficient, after 14 years this amount should be increased to 38 grams/day [6,12].

Calcium

The requirements of calcium to bone mineralization are the highest in adolescence compared to other life stages. Calcium is the most abundant mineral in the body and, as is not produced endogenously to be ingested daily, to perform two principal functions: It is an integral part of the bone structure (99% of its concentration is found in the bones where supports the growth in length and width), and acts as a reservoir to be released into organic fluids, presenting great metabolic interaction with others elements such as phosphorus and vitamin D. Due to hormonal influences, during puberty males acquire more bone mass than females [12].

Mineral deposition of calcium in bones reaches its peak during the adolescent years and the daily needs are 1300 mg that must be obtained from foods such as milk and dairy products, cabbage and beans. Heavy consume of carbonated soft drinks, caffeine, phytates, oxalates, tannins, alcohol abuse, and use of contraceptive pills can have a significant impact on the rate of bone deposition [12,13].

Iron

Iron needs are determined by the demand for tissue development, increased erythrocyte mass and hemoglobin concentration, and replacement of losses to urine, feces, sweat and menstruation. It is a fundamental element for the expansion of blood volume, for the increase of muscle mass (by the increase in myoglobin) and constitutes an important part of several enzymes [14]. The bioavailability of iron depends on some conditions related to the food source and the digestive process. Heme iron is present in animal foods, such as meat, chicken and fish, and is easily absorbed by the intestinal mucosa without the interference of chemical and/or dietary factors. Its absorption is facilitated by the presence of vitamin C and, but its absorption may be reduced by oxalate, phytate, calcium and phenolic compounds. Up to 18 years old, both boys and girls need 18 mg/day of iron. From 19 years old onwards boys need 10 mg/day, while girls continue to require higher amounts due to menstrual losses. Intestinal loss and shedding of skin and other epithelial cells are also pathways of iron loss [15]. Iron deficiency and iron deficiency anemia has been shown to cause negative impacts to the organism like as decrease learning and work capacity, increase fatigue and growth retardation [16].

Zinc

Zinc is the second micronutrient with the highest concentrations in the human organism being considered a fundamental element for the processes of growth, differentiation and cell division, synthesis of DNA, RNA transcription, sexual maturation and growth of connective tissue, among many others. A normal and balanced diet can offer between 10 and 15 mg/day of zinc. Among the richest foods in this micronutrient, fish, meat, poultry, milk and dairy products stand out that can offer about 80% of that total. Bioavailability must also be considered zinc in these food sources, which can vary from 10% to 30%, depending on different compositions of the diet. Daily requirements vary between 10 and 15 mg [17-19].

Vitamins

Vitamins are involved in many of enzymatic activities associated with the growth process, metabolism of nucleic acids, DNA synthesis, cell replication and the effectiveness of the body's metabolic process [5,20]. Among the main vitamins, usually necessary in small concentrations, some characteristics can be highlighted:

• Vitamin A: foods of animal origin provide preformed vitamin A in active form, while vegetables provide pro-vitamin A in the form of carotene;
• Vitamin D: increased needs in periods of accelerated growth interacting with calcium and phosphorus; exposure to sun light provides some of the vitamin D through photo conversion.
• Folate: is essential for replication and translation of DNA, cell division and protein synthesis.
• Vitamin C: has antioxidant action; is fundamental for collagen production, blood vessel integrity, and the immune response; smoking and use of oral contraceptives on a large scale may reduce serum concentration;
• Vitamin B12: of animal origin, it has effects on the maturation of red blood cells and performs multiple functions in the metabolic pathways necessary for the central and peripheral nervous system.

Water

As the largest component of the human body, water is essential for various functions such as promoting chemical reactions, regulating temperature and excreting harmful substances, among others. At least two liters daily of fluids should be consumed throughout the day, preferably water, avoiding the consumption of sugary drinks. This amount must be increased according to climatic conditions, type of diet and amounts lost in physical activities [6,21].

Alternative diets

The limitation of the consumption of animal products and their derivatives (due to moral, religious, ethics or environmental viewpoints) seems to be one of the common choices for those who wish to improve their health status. However, when this occurs during adolescence, it is necessary to know some details that can compromise the individual's health [22,23]. Among the most adopted alternative diets vegetarianism stands out, although is considered restrictive and those who practice it must be accompanied by an experienced professional [24]. However, the American Dietetic Association considers that well-planned vegetarian diet can satisfy the nutritional needs [25].

The vegetarian diet contains less calories and high dietary fiber which helps in intestinal transit but can reduce the absorption of some micronutrients such as iron, zinc, magnesium, calcium, and some amino acids [26]. While smaller amounts of saturated fat and cholesterol can be considered health benefits, nutritional risks include lack of some essential fatty acids (mainly omega-3 family), vitamin B12, vitamin D, iodine, calcium, and iron [27-29]. Such nutritional inadequacies can be aggravated due to the high demand and the lack of food organization typical of adolescents [30].

The different types of vegetarian diet are: a) lacto vegetarian (eat dairy products; b) egg vegetarian (eat egg); pesco vegetarian (eat fish); lacto egg vegetarian (eat dairy products and egg); vegan (the most restrictive and the one most likely to result in nutrient deficits since it excludes all animal products). Vegetarian adolescents may be at risk if nutrients are found in small amounts and are interfered with absorption due to the high content of inhibitory substances in these foods (phytates, and tannins) [22,24,31].

 


Male


Female




Age (years)


9-13


14-19


9-13


14-19




Energy (kcal)


2280


3150


2070


2370




Carbohyidrate (g)


130


130


130


130




Protein (g)


34


52


34


46




Linoleic acid (g)


12


16


10


11




Linolenic acid (g)


1,2


1,6


1,0


1,1




Calcium (mg)


1300


1300


1300


1300




Iron (mg)


8


11


8


15




Zinc (mg)


8


11


8


9




Iodine (µg)


120


150


120


150




Cupper (µg)


700


890


700


890




Magnesium (mg)


240


410


240


360




Fluorine (mg)


2


3


2


3




Folate (µg)


300


400


300


400




Vitamin A (µg)


600


900


600


700




Vitamin C (mg)


45


75


45


65




Vitamin D (µg)


5


5


5


5




Tiamine (mg)


0,9


1,2


0,9


1,0




Riboflavine (mg)


0,9


1,3


0,9


1,0




Niacine (mg)


12


16


12


14




Vitamin B6 (mg)


1,0


1,3


1,0


1,2




Sodium (g)


1,5


1,5


1,5


1,5




Potassium (g)


4,5


4,7


4,5


4,7




Chlorine (g)


2,3


2,3


2,3


2,3




Water (L)


2,4


3,3


2,1


2,3

Appendix: Distribution of nutritional needs and daily intake recommendations during adolescence (Modificated from IOM).